The present invention relates to direct current power supplies and in particular to a power supply that emulates the characteristics of a battery.
An "ideal" power supply is normally defined as having zero impedance. Typically, power supplies are designed with an output impedance as close to zero as is practically possible or economically acceptable. A battery power source will not have a zero impedance and will, in fact, have an impedance that varies with, among other parameters, shelf-life and usage.
A manufacturer of a battery-powered device (e.g., a cellular phone) often will desire to test the device in operation without using a battery. To fully test the device with a power supply as the power source instead of a battery, it is desirable to emulate the voltage-current relationship exhibited by the battery.
In addition, as the power supply will typically be located remotely with respect to the device, it becomes important to be able to control the voltage-current relationship exhibited at the device as opposed to being exhibited at the power supply. For example, the voltage drop caused by the resistance of test leads will alter the voltage-current relationship at the device.